The present invention relates to bending machines, and more particularly concerns automatic machines capable of forming successive bends with different bend dies.
Automatic bending machines such as the machines shown in U.S. Pat. Nos. 3,974,676 and 4,063,441 to Homer Eaton and assigned to Eaton-Leonard Corp., the assignee of the present application, perform a series of program-controlled bends upon a given length of pipe by successively positioning different portions of the pipe adjacent the machine bend head, rotating the bend and clamp dies to form a given bend, releasing the pipe from the bend and clamp dies, advancing and rotating the pipe to the next bend position, and again bending, releasing and advancing until all bends of a series have been completed. In the course of rotation of bend and clamp dies to make a bend, a rearward portion of the pipe is restrained by a pressure die which presses the pipe against a backup member or against the bend die and may exert such a frictional restraint upon the pipe as to effect a draw bending, that is, a stretching of the pipe beyond its yield point as the bend and clamp dies are rotated to pull the pipe forwardly.
The radius of bend made with such a machine is determined by the radius of the tooling or, more specifically, the radius of the bend die. If one bend must be very close to or tangent to another, the bend and clamp dies must be formed with cavities having a compound curvature specific to a given pair of adjacent bends. Therefore, if a bend of a radius different than that of the radius of the bend die then mounted on the machine is desired, or if a different pair of tangent bends is desired, the bending must be stopped and the tooling replaced to position a bend die of different bend form.
Multiple radius and compound curvature bend dies have been employed on manually controlled machines, requiring relatively slow step-by-step procedures for adjustment of the machine and for shifting of the tooling. Separate or individual adjustment of different components of the tooling in prior devices introduce serious problems in maintenance of relative alignment and relative positioning of the various dies and machine parts. Such relative positioning may be critical in performing certain kinds of bends, as for example where the position and pressure exerted by a pressure die controls the amount of pipe stretch in a draw bending operation.
Accordingly, it is an object of the present invention to provide a bending machine capable of performing bends of different curvature without tooling change, while avoiding or minimizing the above-mentioned problems.